Exogenous erythropoietin increases hematological status, fat oxidation, and aerobic performance in males following prolonged strenuous training

This study investigated the effects of EPO on hemoglobin (Hgb) and hematocrit (Hct), time trial (TT) performance, substrate oxidation, and skeletal muscle phenotype throughout 28 days of strenuous exercise. Eight males completed this longitudinal controlled exercise and feeding study using EPO (50 IU/kg body mass) 3×/week for 28 days. Hgb, Hct, and TT performance were assessed PRE and on Days 7, 14, 21, and 27 of EPO. Rested/fasted muscle obtained PRE and POST EPO were analyzed for gene expression, protein signaling, fiber type, and capillarization. Substrate oxidation and glucose turnover were assessed during 90-min of treadmill load carriage (LC; 30% body mass; 55 ± 5% V̇O2peak) exercise using indirect calorimetry, and 6-6-[2H2]-glucose PRE and POST. Hgb and Hct increased, and TT performance improved on Days 21 and 27 compared to PRE (p < 0.05). Energy expenditure, fat oxidation, and metabolic clearance rate during LC increased (p < 0.05) from PRE to POST. Myofiber type, protein markers of mitochondrial biogenesis, and capillarization were unchanged PRE to POST. Transcriptional regulation of mitochondrial activity and fat metabolism increased from PRE to POST (p < 0.05). These data indicate EPO administration during 28 days of strenuous exercise can enhance aerobic performance through improved oxygen carrying capacity, whole-body and skeletal muscle fat metabolism.

Endogenous Glucose Production in Patients With Glycogen Storage Disease Type Ia Estimated by Oral D-[6,6-2H2]-glucose

CONTEXT

Glycogen storage disease type Ia (GSDIa) is an inborn metabolic disorder characterized by impaired endogenous glucose production (EGP). Monitoring of patients with GSDIa is prioritized because of ongoing treatment developments. Stable isotope tracers may enable reliable EGP monitoring.

OBJECTIVE

The aim of this study was to prospectively assess the rate of appearance of endogenous glucose into the bloodstream (Ra) in patients with GSDIa after a single oral D-[6,6-2H2]-glucose dose.

METHODS

Ten adult patients with GSDIa and 10 age-, sex-, and body mass index-matched healthy volunteers (HVs) were enrolled. For each participant, 3 oral glucose tracer tests were performed: (1) preprandial/fasted, (2) postprandial, and (3) randomly fed states. Dried blood spots were collected before D-[6,6-2H2]-glucose administration and 10, 20, 30, 40, 50, 60, 75, 90, and 120 minutes thereafter.

RESULTS

Glucose Ra in fasted HVs was consistent with previously reported data. The time-averaged glucose Ra was significantly higher in (1) preprandial/fasted patients with GSDIa than HV and (2) postprandial HV compared with fasted HV(P < .05). A progressive decrease in glucose Ra was observed in preprandial/fasted patients with GSDIa; the change in glucose Ra time-course was directly correlated with the change in capillary glucose (P < .05).

CONCLUSION

This is the first study to quantify glucose Ra in patients with GSDIa using oral D-[6,6-2H2] glucose. The test can reliably estimate EGP under conditions in which fasting tolerance is unaffected but does not discriminate between relative contributions of EGP (eg, liver, kidney) and exogenous sources (eg, dietary cornstarch). Future application is warranted for longitudinal monitoring after novel genome based treatments in patients with GSDIa in whom nocturnal dietary management can be discontinued.

Acute sub-diaphragmatic anterior vagus nerve stimulation increases peripheral glucose uptake in anaesthetized rats

The sub-diaphragmatic vagus innervates various organs involved in the control of glucose homeostasis including the liver, pancreas and the intestines. In the current study, we investigated the effect of acute electrical stimulation of the anterior trunk of the sub-diaphragmatic vagus on glucose fluxes in anaesthetized adult male rats. After overnight fast, rats underwent either vagus nerve stimulation (VNS+, n = 11; rectangular pulses at 5 Hz, 1.5 mA, 1 msec pulse width) or sham stimulation (VNS-; n = 11) for 120 min under isoflurane anesthesia. Before stimulation, the rats received an i.v. bolus of 1 mL/kg of a sterilized aqueous solution containing 125 mg/mL of D-[6,6-²H₂] glucose. Endogenous glucose production (EGP) and glucose clearance rate (GCR) were calculated by kinetic analysis from the wash-out of injected D-[6,6-²H₂]glucose from the circulation. VNS+ resulted in lower glucose levels compared to the VNS- group (p < 0.05), with similar insulin levels. EGP was similar in both groups, but the GCR was higher in the VNS+ group compared to the VNS- group (p < 0.001). Circulating levels of the sympathetic transmitter norepinephrine were reduced by VNS+ relative to VNS- treatment (p < 0.01). It is concluded that acute anterior sub-diaphragmatic VNS causes stimulation of peripheral glucose uptake, while plasma insulin levels remained similar, and this is associated with lower activity of the sympathetic nervous system.

Pregnane X receptor activation remodels glucose metabolism to promote NAFLD development in obese mice

OBJECTIVE

Both obesity and exposure to chemicals may induce non-alcoholic fatty liver disease (NAFLD). Pregnane X Receptor (PXR) is a central target of metabolism disrupting chemicals and disturbs hepatic glucose and lipid metabolism. We hypothesized that the metabolic consequences of PXR activation may be modified by existing obesity and associated metabolic dysfunction.

METHODS

Wildtype and PXR knockout male mice were fed high-fat diet to induce obesity and metabolic dysfunction. PXR was activated with pregnenolone-16α-carbonitrile. Glucose metabolism, hepatosteatosis, insulin signaling, glucose uptake, liver glycogen, plasma and liver metabolomics, and liver, white adipose tissue, and muscle transcriptomics were investigated.

RESULTS

PXR activation aggravated obesity-induced liver steatosis by promoting lipogenesis and inhibiting fatty acid disposal. Accordingly, hepatic insulin sensitivity was impaired and circulating alanine aminotransferase level increased. Lipid synthesis was facilitated by increased liver glucose uptake and utilization of glycogen reserves resulting in dissociation of hepatosteatosis and hepatic insulin resistance from the systemic glucose tolerance and insulin sensitivity. Furthermore, glucagon-induced hepatic glucose production was impaired. PXR deficiency did not protect from the metabolic manifestations of obesity, but the liver transcriptomics and metabolomics profiling suggest diminished activation of inflammation and less prominent changes in the overall metabolite profile.

CONCLUSIONS

Obesity and PXR activation by chemical exposure have a synergistic effect on NAFLD development. To support liver fat accumulation the PXR activation reorganizes glucose metabolism that seemingly improves systemic glucose metabolism. This implies that obese individuals, already predisposed to metabolic diseases, may be more susceptible to harmful metabolic effects of PXR-activating drugs and environmental chemicals.

Hyperglycaemia, pregnancy outcomes and maternal metabolic disease risk during pregnancy and lactation in a lean gestational diabetes mouse model

Hyperglycaemia in pregnancy (HIP) is a pregnancy complication characterized by mild to moderate hyperglycaemia that negatively impacts short- and long-term health of mother and child. However, relationships between severity and timing of pregnancy hyperglycaemia and postpartum outcomes have not been systemically investigated. We investigated the impact of hyperglycaemia developing during pregnancy (gestational diabetes mellitus, GDM) or already present pre-mating (pre-gestational diabetes mellitus, PDM) on maternal health and pregnancy outcomes. GDM and PDM were induced in C57BL/6NTac mice by combined 60% high fat diet (HF) and low dose streptozotocin (STZ). Animals were screened for PDM prior to mating, and all underwent an oral glucose tolerance test on gestational day (GD)15. Tissues were collected at GD18 or at postnatal day (PN)15. Among HFSTZ-treated dams, 34% developed PDM and 66% developed GDM, characterized by impaired glucose-induced insulin release and inadequate suppression of endogenous glucose production. No increased adiposity or overt insulin resistance was observed. Furthermore, markers of non-alcoholic fatty liver disease (NAFLD) were significantly increased in PDM at GD18 and were positively correlated with basal glucose levels at GD18 in GDM dams. By PN15, NAFLD markers were also increased in GDM dams. Only PDM affected pregnancy outcomes such as litter size. Our findings indicate that GDM and PDM, resulting in disturbances of maternal glucose homeostasis, increase the risk of postpartum NAFLD development, related to the onset and severity of pregnancy hyperglycaemia. These findings signal a need for earlier monitoring of maternal glycaemia and more rigorous follow-up of maternal health after GDM and PDM pregnancy in humans. KEY POINTS: We studied the impact of high-fat diet/streptozotocin induced hyperglycaemia in pregnancy in mice and found that this impaired glucose tolerance and insulin release. Litter size and embryo survival were compromised by pre-gestational, but not by gestational, diabetes. Despite postpartum recovery from hyperglycaemia in a majority of dams, liver disease markers were further elevated by postnatal day 15. Maternal liver disease markers were associated with the severity of hyperglycaemia at gestational day 18. The association between hyperglycaemic exposure and non-alcoholic fatty liver disease signals a need for more rigorous monitoring and follow-up of maternal glycaemia and health in diabetic pregnancy in humans.

Intestinal Farnesoid X Receptor Modulates Duodenal Surface Area but Does Not Control Glucose Absorption in Mice

Bile acids facilitate the intestinal absorption of dietary lipids and act as signalling molecules in the maintenance of metabolic homeostasis. Farnesoid X receptor (FXR) is a bile acid-responsive nuclear receptor involved in bile acid metabolism, as well as lipid and glucose homeostasis. Several studies have suggested a role of FXR in the control of genes regulating intestinal glucose handling. We applied a novel dual-label glucose kinetic approach in intestine-specific FXR^-/- mice (iFXR-KO) to directly assess the role of intestinal FXR in glucose absorption. Although iFXR-KO mice showed decreased duodenal expression of hexokinase 1 (Hk1) under obesogenic conditions, the assessment of glucose fluxes in these mice did not show a role for intestinal FXR in glucose absorption. FXR activation with the specific agonist GS3972 induced Hk1, yet the glucose absorption rate remained unaffected. FXR activation increased the duodenal villus length in mice treated with GS3972, while stem cell proliferation remained unaffected. Accordingly, iFXR-KO mice on either chow, short or long-term HFD feeding displayed a shorter villus length in the duodenum compared to wild-type mice. These findings indicate that delayed glucose absorption reported in whole-body FXR^-/- mice is not due to the absence of intestinal FXR. Yet, intestinal FXR does have a role in the small intestinal surface area.

14-Deoxygarcinol improves insulin sensitivity in high-fat diet-induced obese mice via mitigating NF-κB/Sirtuin 2-NLRP3-mediated adipose tissue remodeling

Interleukin (IL)-1β is a culprit of adipose tissue inflammation, which in turn causes systematic inflammation and insulin resistance in obese individuals. IL-1β is mainly produced in monocytes and macrophages and marginally in adipocytes, through cleavage of the inactive pro-IL-1β precursor by caspase-1, which is activated via the NLRP3 inflammasome complex. The nuclear factor-κB (NF-κB) transcription factor is the master regulator of inflammatory responses. Brindle berry (Garcinia cambogia) has been widely used as health products for treating obesity and related metabolic disorders, but its active principles remain unclear. We previously found a series of polyisoprenylated benzophenones from brindle berry with anti-inflammatory activities. In this study we investigated whether 14-deoxygarcinol (DOG), a major polyisoprenylated benzophenone from brindle berry, alleviated adipose tissue inflammation and insulin sensitivity in high-fat diet fed mice. The mice were administered DOG (2.5, 5 mg · kg-1 · d-1, i.p.) for 4 weeks. We showed that DOG injection dose-dependently improved insulin resistance and hyperlipidemia, but not adiposity in high-fat diet-fed mice. We found that DOG injection significantly alleviated adipose tissue inflammation via preventing macrophage infiltration and pro-inflammatory polarization of macrophages, and adipose tissue fibrosis via reducing the abnormal deposition of extracellular matrix. In LPS plus nigericin-stimulated THP-1 macrophages, DOG (1.25, 2.5, 5 μM) dose-dependently suppressed the activation of NLRP3 inflammasome and NF-κB signaling pathway. We demonstrated that DOG bound to and activated the deacetylase Sirtuin 2, which in turn deacetylated and inactivated NLRP3 inflammasome to reduce IL-1β secretion. Moreover, DOG (1.25, 2.5, 5 μM) dose-dependently mitigated inflammatory responses in macrophage conditioned media-treated adipocytes and suppressed macrophage migration toward adipocytes. Taken together, DOG might be a drug candidate to treat metabolic disorders through modulation of adipose tissue remodeling.

Galactose in the Post-Weaning Diet Programs Improved Circulating Adiponectin Concentrations and Skeletal Muscle Insulin Signaling

Short-term post-weaning nutrition can result in long-lasting effects in later life. Partial replacement of glucose by galactose in the post-weaning diet showed direct effects on liver inflammation. Here, we examined this program on body weight, body composition, and insulin sensitivity at the adult age. Three-week-old female C57BL/6JRccHsd mice were fed a diet with glucose plus galactose (GAL; 16 energy% (en%) each) or a control diet with glucose (GLU; 32 en%) for three weeks, and afterward, both groups were given the same high-fat diet (HFD). After five weeks on a HFD, an oral glucose tolerance test was performed. After nine weeks on a HFD, energy metabolism was assessed by indirect calorimetry, and fasted mice were sacrificed fifteen minutes after a glucose bolus, followed by serum and tissue analyses. Body weight and body composition were not different between the post-weaning dietary groups, during the post-weaning period, or the HFD period. Glucose tolerance and energy metabolism in adulthood were not affected by the post-weaning diet. Serum adiponectin concentrations were significantly higher (p = 0.02) in GAL mice while insulin, leptin, and insulin-like growth factor 1 concentrations were not affected. Expression of Adipoq mRNA was significantly higher in gonadal white adipose tissue (gWAT; p = 0.03), while its receptors in the liver and skeletal muscles remained unaffected. Irs2 expression was significantly lower in skeletal muscles (p = 0.01), but not in gWAT or Irs1 expression (in both tissues). Gene expressions of inflammatory markers in gWAT and the liver were also not affected. Conclusively, galactose in the post-weaning diet significantly improved circulating adiponectin concentrations and reduced skeletal muscle Irs2 expression in adulthood without alterations in fat mass, glucose tolerance, and inflammation.

DPP-4 inhibition mediated antidiabetic potential of phytoconstituents of an aqueous fruit extract of Withania coagulans (Stocks) Dunal: in-silico, in-vitro and in-vivo assessments

The DPP-4 inhibition is an interesting target for the development of antidiabetic agents which promotes the longevity of GPL-1(Glucagon-like peptide 1). The current study was intended to assess DPP-4(Dipeptidyl Peptidase-4) inhibition mediated antidiabetic effect of phytocompounds of an aqueous fruit extract of Withania coagulans (Stocks) Dunal by in-vitro, in-silico and in-vivo approaches. The phytoconstituents screening was executed by LCMS (Liquid Chromatography with tandem mass spectrometry). The in-vitro and in-vivo, DPP-4 assays were performed by using available kits. The in-vitro DPP-4 activity was inhibited up to 68.3% by the test extract. Accordingly, in-silico determinations of molecular docking, molecular dynamics and pharmacokinetics were performed between the target enzyme DPP-4 and leading phytocompounds. The molecular dynamics authenticated the molecular docking data by crucial parameters of cytosolic milieu by the potential energy, RSMD (Root Mean Square Deviation), RSMF (Root Mean Square Fluctuation), system density, NVT (Number of particles at fixed volume, ensemble) and NPT (Number of particles at fixed pressure, ensemble). Accordingly, ADMET predictions assessed the druggability profile. Subsequently, the course of the test extract and the sitagliptin (positive control), instigated significant (p ≤ 0.001) ameliorations in HOMA indices and the equal of antioxidants in nicotinamide-streptozotocin induced type 2 diabetic animal model. Compassionately, the histopathology represented increased pancreatic cellular mass which caused in restoration of histoarchitectures. It has been concluded that phytoconstituents in W. coagulans aqueous fruit extract can regulate DPP-4, resulting in improved glucose homeostasis and enhanced endocrinal pancreatic cellular mass.Communicated by Ramaswamy H. Sarma.

Dynamic Methods for Childhood Hypoglycemia Phenotyping: A Narrative Review

Hypoglycemia results from an imbalance between glucose entering the blood compartment and glucose demand, caused by a defect in the mechanisms regulating postprandial glucose homeostasis. Hypoglycemia represents one of the most common metabolic emergencies in childhood, potentially leading to serious neurologic sequelae, including death. Therefore, appropriate investigation of its specific etiology is paramount to provide adequate diagnosis, specific therapy and prevent its recurrence. In the absence of critical samples for biochemical studies, etiological assessment of children with hypoglycemia may include dynamic methods, such as in vivo functional tests, and continuous glucose monitoring. By providing detailed information on actual glucose fluxes in vivo, proof-of-concept studies have illustrated the potential (clinical) application of dynamic stable isotope techniques to define biochemical and clinical phenotypes of inherited metabolic diseases associated with hypoglycemia. According to the textbooks, individuals with glycogen storage disease type I (GSD I) display the most severe hypoglycemia/fasting intolerance. In this review, three dynamic methods are discussed which may be considered during both diagnostic work-up and monitoring of children with hypoglycemia: 1) functional in vivo tests; 2) in vivo metabolic profiling by continuous glucose monitoring (CGM); 3) stable isotope techniques. Future applications and benefits of dynamic methods in children with hypoglycemia are also discussed.

Generation and characterization of a mouse model for one anastomosis gastric bypass surgery

One anastomosis gastric bypass (OAGB) surgery became a common bariatric procedure in recent years. In this surgery, the distal stomach, duodenum, and proximal jejunum are bypassed, leading to weight loss, improvement in metabolic parameters, and a change in hormonal secretion. We sought to generate and characterize a mouse model for OAGB. Mice fed for 26 wk on a high-fat diet were assigned to OAGB, sham surgery, or caloric restriction and were followed for 50 more days on a high-fat diet. Physiological and histological parameters of the mice were compared during and at the end of the experiment. OAGB-operated mice lost weight and displayed low levels of plasma lipids, high insulin sensitivity, and rapid glucose metabolism compared with sham-operated mice. OAGB-operated mice had higher energy expenditure, higher levels of glucagon-like peptide (GLP-1), and lower albumin than weight-matched calorie-restricted mice. There was no difference in the histology of the endocrine pancreas. The livers of OAGB mice had little hepatic steatosis yet presented with a large number of phagocytic cells. The OAGB mouse model recapitulates many of the phenotypes described in patients that underwent OAGB and enables molecular and physiological studies on the outcome of this surgery.NEW & NOTEWORTHY A mouse model for one anastomosis gastric bypass (OAGB) surgery displays similar outcomes to clinical reports and enables to study the weight loss-dependent and -independent effects of this bariatric surgery.

The female mouse is resistant to mild vitamin B3 deficiency

Purpose

Vitamin B₃ provides nicotinamide adenine dinucleotide (NAD⁺), an essential coenzyme in oxidoreductase reactions. Severe vitamin B₃ deficiency leads to the disease Pellagra, while mild vitamin B₃ deficiency has been linked to age-related and metabolic diseases. Mild vitamin B₃ deficiency is understudied, especially in females. Therefore, we examined how female mice responded to a diet that induced mild vitamin B₃ deficiency in male mice.

Methods

Female C57BL/6RccHsd mice were subjected for 18 weeks to a diet without vitamin B₃ and low but sufficient tryptophan (0.115%) (0NR) and were compared to control female mice on the same diet with the reference dose of vitamin B₃ (30NR, 30 mg nicotinamide riboside/ kg diet).

Results

In the female mice, no differences between the two dietary groups were found in liver nicotinamide mononucleotide (NMN) levels, body composition, whole body energy and substrate metabolism measured by indirect calorimetry, or liver triacylglycerol metabolism. Expression of seven genes that previously were shown to respond to mild vitamin B₃ deficiency in male white adipose tissue were not differentially expressed between the female dietary groups, neither was insulin sensitivity.

Conclusion

We concluded that the female 0NR mice were not vitamin B₃ deficient; the role of age, sex and health status is discussed. Demonstrated by clear differences between females and males, the latter showing mild deficiency under the same conditions, this study highlights the importance of studying both sexes.

Supplementary Information

The online version contains supplementary material available at 10.1007/s00394-021-02651-8.

Age-related susceptibility to insulin resistance arises from a combination of CPT1B decline and lipid overload

BACKGROUND

The skeletal muscle plays a central role in glucose homeostasis through the uptake of glucose from the extracellular medium in response to insulin. A number of factors are known to disrupt the normal response to insulin leading to the emergence of insulin resistance (IR). Advanced age and a high-fat diet are factors that increase the susceptibility to IR, with lipid accumulation in the skeletal muscle being a key driver of this phenomenon. It is debated, however, whether lipid accumulation arises due to dietary lipid overload or from a decline of mitochondrial function. To gain insights into the interplay of diet and age in the flexibility of muscle lipid and glucose handling, we combined lipidomics, proteomics, mitochondrial function analysis and computational modelling to investigate young and aged mice on a low- or high-fat diet (HFD).

RESULTS

As expected, aged mice were more susceptible to IR when given a HFD than young mice. The HFD induced intramuscular lipid accumulation specifically in aged mice, including C18:0-containing ceramides and diacylglycerols. This was reflected by the mitochondrial β-oxidation capacity, which was upregulated by the HFD in young, but not in old mice. Conspicuously, most β-oxidation proteins were upregulated by the HFD in both groups, but carnitine palmitoyltransferase 1B (CPT1B) declined in aged animals. Computational modelling traced the flux control mostly to CPT1B, suggesting a CPT1B-driven loss of flexibility to the HFD with age. Finally, in old animals, glycolytic protein levels were reduced and less flexible to the diet.

CONCLUSION

We conclude that intramuscular lipid accumulation and decreased insulin sensitivity are not due to age-related mitochondrial dysfunction or nutritional overload alone, but rather to their combined effects. Moreover, we identify CPT1B as a potential target to counteract age-dependent intramuscular lipid accumulation and thereby IR.

Short-term protein restriction at advanced age stimulates FGF21 signalling, energy expenditure and browning of white adipose tissue

Dietary protein restriction has been demonstrated to improve metabolic health under various conditions. However, the relevance of ageing and age-related decline in metabolic flexibility on the effects of dietary protein restriction has not been addressed. Therefore, we investigated the effect of short-term dietary protein restriction on metabolic health in young and aged mice. Young adult (3 months old) and aged (18 months old) C57Bl/6J mice were subjected to a 3-month dietary protein restriction. Outcome parameters included fibroblast growth factor 21 (FGF21) levels, muscle strength, glucose tolerance, energy expenditure (EE) and transcriptomics of brown and white adipose tissue (WAT). Here, we report that a low-protein diet had beneficial effects in aged mice by reducing some aspects of age-related metabolic decline. These effects were characterized by increased plasma levels of FGF21, browning of subcutaneous WAT, increased body temperature and EE, while no changes were observed in glucose homeostasis and insulin sensitivity. Moreover, the low-protein diet used in this study was well-tolerated in aged mice indicated by the absence of adverse effects on body weight, locomotor activity and muscle performance. In conclusion, our study demonstrates that a short-term reduction in dietary protein intake can impact age-related metabolic health alongside increased FGF21 signalling, without negatively affecting muscle function. These findings highlight the potential of protein restriction as a strategy to induce EE and browning of WAT in aged individuals.

Increased insulin sensitivity and diminished pancreatic beta-cell function in DNA repair deficient Ercc1d/- mice

BACKGROUND

Type 2 diabetes (T2DM) is an age-associated disease characterized by hyperglycemia due to insulin resistance and decreased beta-cell function. DNA damage accumulation has been associated with T2DM, but whether DNA damage plays a role in the pathogenesis of the disease is unclear. Here, we used mice deficient for the DNA excision-repair gene Ercc1 to study the impact of persistent endogenous DNA damage accumulation on energy metabolism, glucose homeostasis and beta-cell function.

METHODS

ERCC1-XPF is an endonuclease required for multiple DNA repair pathways and reduced expression of ERCC1-XPF causes accelerated accumulation of unrepaired endogenous DNA damage and accelerated aging in humans and mice. In this study, energy metabolism, glucose metabolism, beta-cell function and insulin sensitivity were studied in Ercc1^d/- mice, which model a human progeroid syndrome.

RESULTS

Ercc1^d/- mice displayed suppression of the somatotropic axis and altered energy metabolism. Insulin sensitivity was increased, whereas, plasma insulin levels were decreased in Ercc1^d/- mice. Fasting induced hypoglycemia in Ercc1^d/- mice, which was the result of increased glucose disposal. Ercc1^d/- mice exhibit a significantly reduced beta-cell area, even compared to control mice of similar weight. Glucose-stimulated insulin secretion in vivo was decreased in Ercc1^d/- mice. Islets isolated from Ercc1^d/- mice showed increased DNA damage markers, decreased glucose-stimulated insulin secretion and increased susceptibility to apoptosis.

CONCLUSION

Spontaneous DNA damage accumulation triggers an adaptive response resulting in improved insulin sensitivity. Loss of DNA repair, however, does negatively impacts beta-cell survival and function in Ercc1^d/- mice.

Choice of Lipid Emulsion Determines Inflammation of the Gut-Liver Axis, Incretin Profile, and Insulin Signaling in a Murine Model of Total Parenteral Nutrition

SCOPE

The aim of this study is to test whether the choice of the lipid emulsion in total parenteral nutrition (TPN), that is, n-3 fatty acid-based Omegaven versus n-6 fatty acid-based Intralipid, determines inflammation in the liver, the incretin profile, and insulin resistance.

METHODS AND RESULTS

Jugular vein catheters (JVC) are placed in C57BL/6 mice and used for TPN for 7 days. Mice are randomized into a saline group (saline infusion with oral chow), an Intralipid group (IL-TPN, no chow), an Omegaven group (OV-TPN, no chow), or a chow only group (without JVC). Both TPN elicite higher abundance of lipopolysaccharide binding protein in the liver, but only IL-TPN increases interleukin-6 and interferon-γ, while OV-TPN reduces interleukin-4, monocyte chemoattractant protein-1, and interleukin-1α. Insulin plasma concentrations are higher in both TPN, while glucagon and glucagon-like peptide-1 (GLP-1) were higher in IL-TPN. Gluconeogenesis is increased in IL-TPN and the nuclear profile of key metabolic transcription factors shows a liver-protective phenotype in OV-TPN. OV-TPN increases insulin sensitivity in the liver and skeletal muscle.

CONCLUSION

OV-TPN as opposed to IL-TPN mitigates inflammation in the liver and reduces the negative metabolic effects of hyperinsulinemia and hyperglucagonemia by "re-sensitizing" the liver and skeletal muscle to insulin.

Discovery of : A Novel Potent and Peripherally Preferred Melatonin Receptor Agonist that Reduces Liver Triglycerides and Steatosis in Diet-Induced Obese Rats

The modulation of melatonin signaling in peripheral tissues holds promise for treating metabolic diseases like obesity, diabetes, and nonalcoholic steatohepatitis. Here, several benzimidazole derivatives have been identified as novel agonists of the melatonin receptors MT1 and MT2. The lead compounds 10b, 15a, and 19a demonstrated subnanomolar potency at MT1/MT2 receptors, high oral bioavailability in rodents, peripherally preferred exposure, and excellent selectivity in a broad panel of targets. Two-month oral administration of 10b in high-fat diet rats led to a reduction in body weight gain similar to dapagliflozin with superior results on hepatic steatosis and triglyceride levels. An early toxicological assessment indicated that 10b (also codified as ACH-000143) was devoid of hERG binding, genotoxicity, and behavioral alterations at doses up to 100 mg/kg p.o., supporting further investigation of this compound as a drug candidate.

Multigenerational study of the obesogen effects of bisphenol S after a perinatal exposure in C57BL6/J mice fed a high fat diet

BACKGROUND

Bisphenol S is an endocrine disruptor exhibiting metabolic disturbances, especially following perinatal exposures. To date, no data are available on the obesogen effects of BPS in a mutligenerational issue.

OBJECTIVES

We investigated obesogen effects of BPS in a multigenerational study by focusing on body weight, adipose tissue and plasma parameters in male and female mice.

METHODS

Pregnant C57BL6/J mice were exposed to BPS (1.5 μg/kg bw/day ie a human equivalent dose of 0.12 μg/kg bw/day) by drinking water from gestational day 0 to post natal day 21. All offsprings were fed with a high fat diet during 15 weeks. Body weight was monitored weekly and fat mass was measured before euthanasia. At euthanasia, blood glucose, insuline, triglyceride, cholesterol and no esterified fatty acid plasma levels were determined and gene expressions in visceral adipose tissue were assessed. F1 males and females were mated to obtain the F2 generation. Likewise, the F2 mice were cross-bred to obtain F3. The same analyses were performed.

RESULTS

In F1 BPS induced an overweight in male mice associated to lipolysis gene expressions upregulation. In F1 females, dyslipidemia was observed. In F2, BPS exposure was associated to an increase in body weight, fat and VAT masses in males and females. Several plasma parameters were increased but with a sex related pattern (blood glucose, triglycerides and cholesterol in males and NEFA in females). We observed a down-regulation in mRNA expression of gene involved in lipogenesis and in lipolysis for females but only in the lipogenesis for males. In F3, a decrease in VAT mass and an upregulation of lipogenesis gene expression occurred only in females.

CONCLUSIONS

BPS perinatal exposure induced sex-dependent obesogen multigenerational effects, the F2 generation being the most impacted. Transgenerational disturbances persisted only in females.

DNA aptamer raised against receptor for advanced glycation end products suppresses renal tubular damage and improves insulin resistance in diabetic mice

OBJECTIVE

Interaction of advanced glycation end products (AGEs) with the receptor RAGE plays a role in diabetic nephropathy. However, effects of RAGE-aptamer on tubular damage remain unknown. We examined whether RAGE-aptamer inhibited tubular damage in KKAy/Ta mice, obese type 2 diabetic mice with insulin resistance.

MATERIALS AND METHODS

Male 8-week-old KKAy/Ta mice received continuous intraperitoneal infusion of either control-aptamer or RAGE-aptamer for 8 weeks. Blood biochemistry and blood pressure, and urinary N-acetyl-β-D-glucosaminidase (NAG) activity and albumin excretion levels were monitored. Kidney and adipose tissue samples were obtained for immunohistochemical analyses.

RESULTS

Although RAGE-aptamer did not affect blood glucose, blood pressure, body weight, or serum creatinine values, it significantly inhibited the increase in urinary NAG activity and HOMA-IR in diabetic mice at 12 and 16 and at 16 weeks old, respectively. Furthermore, compared with control-aptamer-treated mice, renal carboxymethyllysine, RAGE, and NADPH oxidase-driven superoxide generation were significantly decreased in RAGE-aptamer-treated mice at 12 weeks old with subsequent amelioration of histological alterations in glomerular and interstitial area, while adipose tissue adiponectin expression was increased.

CONCLUSION

Our present results suggest that RAGE-aptamer could inhibit tubular injury in obese type 2 diabetic mice partly by suppressing the AGE-RAGE-oxidative stress axis and improving insulin resistance.

Antioxidant Effects of N-Acetylcysteine Prevent Programmed Metabolic Disease in Mice

An adverse maternal in utero and lactation environment can program offspring for increased risk for metabolic disease. The aim of this study was to determine whether N-acetylcysteine (NAC), an anti-inflammatory antioxidant, attenuates programmed susceptibility to obesity and insulin resistance in offspring of mothers on a high-fat diet (HFD) during pregnancy. CD1 female mice were acutely fed a standard breeding chow or HFD. NAC was added to the drinking water (1 g/kg) of the treatment cohorts from embryonic day 0.5 until the end of lactation. NAC treatment normalized HFD-induced maternal weight gain and oxidative stress, improved the maternal lipidome, and prevented maternal leptin resistance. These favorable changes in the in utero environment normalized postnatal growth, decreased white adipose tissue (WAT) and hepatic fat, improved glucose and insulin tolerance and antioxidant capacity, reduced leptin and insulin, and increased adiponectin in HFD offspring. The lifelong metabolic improvements in the offspring were accompanied by reductions in proinflammatory gene expression in liver and WAT and increased thermogenic gene expression in brown adipose tissue. These results, for the first time, provide a mechanistic rationale for how NAC can prevent the onset of metabolic disease in the offspring of mothers who consume a typical Western HFD.

Running wheel access fails to resolve impaired sustainable health in mice feeding a high fat sucrose diet

Diet and physical activity are thought to affect sustainable metabolic health and survival. To improve understanding, we studied survival of mice feeding a low-fat (LF) or high-saturated fat/high sugar (HFS) diet, each with or without free running wheel (RW) access. Additionally several endocrine and metabolic health indices were assessed at 6, 12, 18 and 24 months of age. As expected, HFS feeding left-shifted survival curve of mice compared to LF feeding, and this was associated with increased energy intake and increased (visceral/total) adiposity, liver triglycerides, and increased plasma cholesterol, corticosterone, HOMA-IR, and lowered adiponectin levels. Several of these health parameters improved (transiently) by RW access in HFS and LF fed mice (i.e., HOMA-IR, plasma corticosterone), others however deteriorated (transiently) by RW access only in HFS-fed mice (i.e., body adiposity, plasma resistin, and free cholesterol levels). Apart from these multiple and sometimes diverging health effects of RW access, RW access did not affect survival curves. Important to note, voluntary RW activity declined with age, but this effect was most pronounced in the HFS fed mice. These results thus challenge the hypothesis that voluntary wheel running can counteract HFS-induced deterioration of survival and metabolic health.

Nesfatin-1 ameliorates type-2 diabetes-associated reproductive dysfunction in male mice

PURPOSE

The present study was aimed to demonstrate the recuperative effect of nesfatin-1 on testicular dysfunction in the high-fat diet (HFD)/streptozotocin (STZ)-induced type-2 diabetes mellitus (T2DM) mice.

METHOD AND RESULTS

Three experimental groups were formed: (1) vehicle control (VC), (2) T2DM mice, (3) T2DM + nesf-1. The mice with blood glucose level higher than 300 mg/dL following HFD and a single dose of STZ were used for the experiment. The T2DM mice showed increases in body mass, blood glucose and insulin levels, reductions in spermatogenesis and steroidogenesis, production of antioxidative enzymes, and disturbed lipid profile. These alterations were all ameliorated by administration of nesfatin-1 at 20 μg/Kg BW for 15 days. Nesfatin-1 treatment also increased the production of testosterone (T), improved insulin sensitivity, and effectively ameliorated the testicular aberrations, and increased spermatogenesis and steroidogenesis. In addition, nesfatin-1 treatment upregulated the PCNA and Bcl2 expression and inhibited the caspase-3 and prohibitin expression in T2DM mice. Nesfatin-1 increased insulin receptor (IR) and GLUT8 expressions, and lactate production, the changes that further substantiate the increase of energy influx to the testis.

CONCLUSION

Altogether, the results suggest the ameliorative effect of nesfatin-1 against T2DM-associated testicular dysfunctions and improved insulin sensitivity along with promoting T production and fertility in T2DM mice.

TNF-Receptor-1 inhibition reduces liver steatosis, hepatocellular injury and fibrosis in NAFLD mice

Non-alcoholic fatty liver disease (NAFLD) shows an increasing prevalence and is associated with the development of liver fibrosis and cirrhosis as the major risk factors of liver-related mortality in this disease. The therapeutic possibilities are limited and restricted to life style intervention, since specific drugs for NAFLD are unavailable so far. TNFα has been implicated as a major pathogenic driver of NAFLD. TNFα-mediated liver injury occurs mainly via TNF-receptor-1 (TNFR1) signaling, whereas TNFR2 mediates protective pathways. In this study, we analyzed the therapeutic effects of a novel antibody, which selectively inhibits TNFR1 while retaining protective TNFR2 signaling in a high-fat diet (HFD) mouse model of NAFLD. Mice were fed with HFD for 32 weeks and treated with anti-TNFR1-antibody or control-antibody for the last 8 weeks. We then investigated the mechanisms of TNFR1 inhibition on liver steatosis, inflammatory liver injury, insulin resistance and fibrosis. Compared to control-antibody treatment, TNFR1 inhibition significantly reduced liver steatosis and triglyceride content, which was accompanied by reduced expression and activation of the transcription factor SREBP1 and downstream target genes of lipogenesis. Furthermore, inhibition of TNFR1 resulted in reduced activation of the MAP kinase MKK7 and its downstream target JNK, which was associated with significant improvement of insulin resistance. Apoptotic liver injury, NAFLD activity and alanine aminotransferase (ALT) levels, as well as liver fibrosis significantly decreased by anti-TNFR1 compared to control-antibody treatment. Thus, our results suggest selective TNFR1 inhibition as a promising approach for NAFLD treatment.

Modelling the Impact of Chronic Cigarette Smoke Exposure in Obese Mice: Metabolic, Pulmonary, Intestinal, and Cardiac Issues

Unhealthy lifestyle choices, such as bad eating behaviors and cigarette smoking, have major detrimental impacts on health. However, the inter-relations between obesity and smoking are still not fully understood. We thus developed an experimental model of high-fat diet-fed obese C57BL/6 male mice chronically exposed to cigarette smoke. Our study evaluated for the first time the resulting effects of the combined exposure to unhealthy diet and cigarette smoke on several metabolic, pulmonary, intestinal, and cardiac parameters. We showed that the chronic exposure to cigarette smoke modified the pattern of body fat distribution in favor of the visceral depots in obese mice, impaired the respiratory function, triggered pulmonary inflammation and emphysema, and was associated with gut microbiota dysbiosis, cardiac hypertrophy and myocardial fibrosis.

Metabolic effects of the dietary monosaccharides fructose, fructose-glucose, or glucose in mice fed a starch-containing moderate high-fat diet

Fructose consumption has been linked to obesity and increased hepatic de novo lipogenesis (DNL). Excessive caloric intake often confounds the results of fructose studies, and experimental diets are generally low-fat diets, not representative for westernized diets. Here, we compared the effects of dietary fructose with those of dietary glucose, in adult male and female mice on a starch-containing moderate high-fat (HF) diet. After 5 weeks fattening on a HF high-glucose (HF-G) diet, mice were stratified per sex and assigned to one of the three intervention diets for 6 weeks: HF high fructose (HF-F), HF with equimolar glucose and fructose (HF-GF), or HF-G. Bodyweight (BW) and food intake were measured weekly. Indirect calorimetry was performed on week 5; animals were sacrificed in food-deprived state on week 6. Data were analyzed within sex. BW gain was similar among animals on the HF-G, HF-GF, and HF-F diets. Cumulative food intake was slightly lower in HF-F animals (both sexes). However, energy expenditure was not affected, or were circulating insulin and glucose concentrations, and hepatic triglyceride levels at endpoint. Hepatic gene expression analysis showed only minor alterations in hexokinase and glycolysis-related expression in males, and no alterations in sugar transporters, or DNL-related enzymes. In females, no consistent alterations in hepatic or small intestine gene expression were seen. Concluding, partial or complete replacement of dietary glucose with fructose does not increase caloric intake, and does not affect BW, hepatic triglyceride levels, or insulin concentrations in male and female mice on a moderate high-fat diet.

Disruption of Acetyl-Lysine Turnover in Muscle Mitochondria Promotes Insulin Resistance and Redox Stress without Overt Respiratory Dysfunction

This study sought to examine the functional significance of mitochondrial protein acetylation using a double knockout (DKO) mouse model harboring muscle-specific deficits in acetyl-CoA buffering and lysine deacetylation, due to genetic ablation of carnitine acetyltransferase and Sirtuin 3, respectively. DKO mice are highly susceptible to extreme hyperacetylation of the mitochondrial proteome and develop a more severe form of diet-induced insulin resistance than either single KO mouse line. However, the functional phenotype of hyperacetylated DKO mitochondria is largely normal. Of the >120 measures of respiratory function assayed, the most consistently observed traits of a markedly heightened acetyl-lysine landscape are enhanced oxygen flux in the context of fatty acid fuel and elevated rates of electron leak. In sum, the findings challenge the notion that lysine acetylation causes broad-ranging damage to mitochondrial quality and performance and raise the possibility that acetyl-lysine turnover, rather than acetyl-lysine stoichiometry, modulates redox balance and carbon flux.

Key Concepts Surrounding Studies of Stable Isotope-Resolved Metabolomics

"Omics"-based analyses are widely used in numerous areas of research, advances in instrumentation (both hardware and software) allow investigators to collect a wealth of data and therein characterize metabolic systems. Although analyses generally examine differences in absolute or relative (fold-) changes in concentrations, the ability to extract mechanistic insight would benefit from the use of isotopic tracers. Herein, we discuss important concepts that should be considered when stable isotope tracers are used to capture biochemical flux. Special attention is placed on in vivo systems, however, many of the general ideas have immediate impact on studies in cellular models or isolated-perfused tissues. While it is somewhat trivial to administer labeled precursor molecules and measure the enrichment of downstream products, the ability to make correct interpretations can be challenging. We will outline several critical factors that may influence choices when developing and/or applying a stable isotope tracer method. For example, is there a "best" tracer for a given study? How do I administer a tracer? When do I collect my sample(s)? While these questions may seem straightforward, we will present scenarios that can have dramatic effects on conclusions surrounding apparent rates of metabolic activity.

Partial replacement of glucose by galactose in the post-weaning diet improves parameters of hepatic health

Replacing part of glucose with galactose in the post-weaning diet beneficially affects later life metabolic health in female mice. The liver is the main site of galactose metabolism, but the direct effects of this dietary intervention on the liver in the post-weaning period are not known. The aim of this study was to elucidate this. Weanling female mice (C57BL/6JRccHsd) were fed a starch containing diet with glucose (32 en%) monosaccharide (GLU), or a diet with glucose and galactose (1:1 both 16 en%) (GLU+GAL). Body weight, body composition, and food intake were determined weekly. After 3 weeks, mice were sacrificed, and serum and liver tissues were collected. Global hepatic mRNA expression was analyzed and hepatic triglyceride (TG) and glycogen contents were determined by enzymatic assays. Body weight and body composition were similar in both groups, despite higher food intake in mice on GLU+GAL diet. Hepatic TG content was lower in GLU+GAL-fed than GLU-fed females, while glycogen levels were unaffected. Analysis of global expression patterns of hepatic mRNA showed that mainly inflammation-related pathways were affected by the diet, which were predominantly downregulated in GLU+GAL-fed females compared to GLU-fed females. This reduction in inflammation in GLU+GAL-fed females was also reflected by decreased serum concentrations of acute phase protein Serum amyloid A 3. In conclusion, replacing part of glucose with galactose in the post-weaning diet reduces hepatic TG content and hepatic inflammation.

High Dose of Dietary Nicotinamide Riboside Induces Glucose Intolerance and White Adipose Tissue Dysfunction in Mice Fed a Mildly Obesogenic Diet

Nicotinamide riboside (NR) is a nicotinamide adenine dinucleotide (NAD⁺) precursor vitamin. The scarce reports on the adverse effects on metabolic health of supplementation with high-dose NR warrant substantiation. Here, we aimed to examine the physiological responses to high-dose NR supplementation in the context of a mildly obesogenic diet and to substantiate this with molecular data. An 18-week dietary intervention was conducted in male C57BL/6JRccHsd mice, in which a diet with 9000 mg NR per kg diet (high NR) was compared to a diet with NR at the recommended vitamin B3 level (control NR). Both diets were mildly obesogenic (40 en% fat). Metabolic flexibility and glucose tolerance were analyzed and immunoblotting, qRT-PCR and histology of epididymal white adipose tissue (eWAT) were performed. Mice fed with high NR showed a reduced metabolic flexibility, a lower glucose clearance rate and aggravated systemic insulin resistance. This was consistent with molecular and morphological changes in eWAT, including sirtuin 1 (SIRT1)-mediated PPARγ (proliferator-activated receptor γ) repression, downregulated AKT/glucose transporter type 4 (GLUT4) signaling, an increased number of crown-like structures and macrophages, and an upregulation of pro-inflammatory gene markers. In conclusion, high-dose NR induces the onset of WAT dysfunction, which may in part explain the deterioration of metabolic health.

Gestational oxidative stress protects against adult obesity and insulin resistance

Pregnancy complications such as preeclampsia cause increased fetal oxidative stress and fetal growth restriction, and associate with a higher incidence of adult metabolic syndrome. However, the pathophysiological contribution of oxidative stress per se is experimentally difficult to discern and has not been investigated. This study determined, if increased intrauterine oxidative stress (IUOx) affects adiposity, glucose and cholesterol metabolism in adult Ldlr−/−xSod2+/+ offspring from crossing male Ldlr−/−xSod2+/+ mice with Ldlr−/−xSod2 +/- dams (IUOx) or Ldlr−/−xSod2 +/- males with Ldlr−/−xSod2+/+ dams (control). At 12 weeks of age mice received Western diet for an additional 12 weeks. Adult male IUOx offspring displayed lower body weight and reduced adiposity associated with improved glucose tolerance compared to controls. Reduced weight gain in IUOx was conceivably due to increased energy dissipation in white adipose tissue conveyed by higher expression of Ucp1 and an accompanying decrease in DNA methylation in the Ucp1 enhancer region. Female offspring did not show comparable phenotypes. These results demonstrate that fetal oxidative stress protects against the obesogenic effects of Western diet in adulthood by programming energy dissipation in white adipose tissue at the level of Ucp1.

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Intrauterine oxidative stress (IUOx) in absence of growth restriction was induced.

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IUOx results in less obesity and improved glucose tolerance in adult male mice.

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Reduced adiposity in adult males is due to browning of white adipose tissue (WAT).

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Increased UCP-1 expression in WAT of IUOx mice is explained by lower methylation.

Glucose metabolism during tumorigenesis in the genetic mouse model of pancreatic cancer

AIM

More than 40% of pancreatic ductal adenocarcinoma (PDAC) patients have glucose intolerance or diabetes. The association has led to two hypotheses: PDAC causes diabetes or diabetes shares risk factors for the development of PDAC. In order to elucidate the relationship between diabetes and PDAC, we investigated the glucose metabolism during tumorigenesis in the LSL-KrasG12D/+; LSL-Trp53R172H/+; and Pdx-1-Cre (KPC) mouse, a genetically engineered model of PDAC.

METHODS

Male and female KPCs have been fed with standard diet (SD) or high-fat diet (HFD). The imaging-based 4-class tumor staging was used to follow pancreatic cancer development. Not fasting glycemia, 4-h fasting glycemia, insulin, C-peptide, glucose tolerance after OGTT and abdominal fat volume were measured during tumorigenesis.

RESULTS

PDAC development did not lead to an overt diabetic phenotype or to any alterations in glucose tolerance in KPC fed with SD. Consumption of HFD induced higher body weight/abdominal fat volume and worsened glucose homeostasis both in control CRE mice and only in early tumorigenesis stages of the KPC mice, excluding that the cancer development itself acts as a trigger for the onset of dysmetabolic features.

CONCLUSION

Our data demonstrate that carcinogenesis in KPC mice is not associated with paraneoplastic diabetes.

FXR overexpression alters adipose tissue architecture in mice and limits its storage capacity leading to metabolic derangements

The bile acid-activated nuclear receptor, FXR (NR1H4), has been implicated in the control of lipid and energy metabolism, but its role in fat tissue, where it is moderately expressed, is not understood. In view of the recent development of FXR-targeting therapeutics for treatment of human metabolic diseases, understanding the tissue-specific actions of FXR is essential. Transgenic mice expressing human FXR in adipose tissue (aP2-hFXR mice) at three to five times higher levels than endogenous Fxr, i.e., much lower than its expression in liver and intestine, have markedly enlarged adipocytes and show extensive extracellular matrix remodeling. Ageing and exposure to obesogenic conditions revealed a strongly limited capacity for adipose expansion and development of fibrosis in adipose tissues of aP2-hFXR transgenic mice. This was associated with impaired lipid storage capacity, leading to elevated plasma free fatty acids and ectopic fat deposition in liver and muscle as well as whole-body insulin resistance. These studies establish that adipose FXR is a determinant of adipose tissue architecture and contributes to whole-body lipid homeostasis.

Replacing Part of Glucose with Galactose in the Postweaning Diet Protects Female But Not Male Mice from High-Fat Diet-Induced Adiposity in Later Life

BACKGROUND

Duration of breastfeeding is positively associated with decreased adiposity and increased metabolic health in later life, which might be related to galactose.

OBJECTIVE

The aim of this study was to investigate if partial replacement of glucose with galactose in the postweaning diet had a metabolic programming effect.

METHODS

Male and female mice (C57BL/6JRccHsd) received an isocaloric diet (16 energy% fat; 64 energy% carbohydrates; 20 energy% protein) with either glucose (32 energy%) (GLU) or glucose + galactose (GLU + GAL, 16 energy% each) for 3 wk postweaning. Afterwards, all mice were switched to the same 40 energy% high-fat diet (HFD) for 9 wk to evaluate potential programming effects in an obesogenic environment. Data were analyzed within sex.

RESULTS

Female body weight (-14%) and fat mass (-47%) were significantly lower at the end of the HFD period (both P < 0.001) among those fed GLU + GAL than among those fed GLU; effects in males were in line with these findings but nonsignificant. Food intake was affected in GLU + GAL-fed females (+8% on postweaning diet, -9% on HFD) compared with GLU-fed females, but not for hypothalamic transcript levels at endpoint. Also, in GLU + GAL-fed females, serum insulin concentrations (-48%, P  < 0.05) and the associated homeostasis model assessment of insulin resistance (HOMA-IR) were significantly lower ( P < 0.05) at endpoint, but there were no changes in pancreas morphology. In GLU + GAL-fed females, expression of insulin receptor substrate 2 (Irs2) (-27%, P  < 0.01 ; -44%, P  < 0.001) and the adipocyte size markers leptin (Lep) (-40%, P  < 0.05; -63% , P  < 0.05) and mesoderm-specific transcript homolog protein (Mest) (-80%, P < 0.05; -72%, P  < 0.05) was lower in gonadal and subcutaneous white adipose tissue (WAT), respectively. Expression of insulin receptor substrate1 (Irs1) (-24%, P  < 0.05) was only lower in subcutaneous WAT in GLU + GAL-fed females.

CONCLUSIONS

Partial replacement of glucose with galactose, resulting in a 1:1 ratio mimicking lactose, in a 3-wk postweaning diet lowered body weight, adiposity, HOMA-IR, and expression of WAT insulin signaling in HFD-challenged female mice in later life. This suggests that prolonged galactose intake may improve metabolic and overall health in later life.

Spatial and temporal studies of metabolic activity: contrasting biochemical kinetics in tissues and pathways during fasted and fed states

The regulation of nutrient homeostasis, i.e., the ability to transition between fasted and fed states, is fundamental in maintaining health. Since food is typically consumed over limited (anabolic) periods, dietary components must be processed and stored to counterbalance the catabolic stress that occurs between meals. Herein, we contrast tissue- and pathway-specific metabolic activity in fasted and fed states. We demonstrate that knowledge of biochemical kinetics that is obtained from opposite ends of the energetic spectrum can allow mechanism-based differentiation of healthy and disease phenotypes. Rat models of type 1 and type 2 diabetes serve as case studies for probing spatial and temporal patterns of metabolic activity via [²H]water labeling. Experimental designs that capture integrative whole body metabolism, including meal-induced substrate partitioning, can support an array of research surrounding metabolic disease; the relative simplicity of the approach that is discussed here should enable routine applications in preclinical models.

Effect of supplementing chromium histidinate and picolinate complexes along with biotin on insulin sensitivity and related metabolic indices in rats fed a high-fat diet

SCOPE

To investigate the effects of chromium histidinate (CrHis) and chromium picolinate (CrPic) complex along with biotin to a high-fat diet (HFD) fed to rats on the insulin sensitivity and the anti-obesity properties.

METHODS

Forty-two Sprague-Dawley male rats were divided into six groups. The rats were fed either (a): a standard diet (Control) or (b): a HFD or (c): a HFD with biotin (HFD+B) or (d): a combination of HFD and biotin along with CrPic (HFD + B + CrPic) or (e): a combination of HFD and biotin along with CrHis (HFD + B + CrHis) or (f): a combination of HFD and biotin along with CrHis and CrPic (HFD + B + CrHis + CrPic).

RESULTS

Adding biotin with chromium to HFD improved the glucose, insulin, HOMA-IR, leptin, lipid profile, with HFD+B+CrHis treatment being the most effective (p = 0.0001). Serum, liver, and brain tissue Cr concentrations increased upon Cr supplementations (p = 0.0001). Supplementing CrHis along with biotin to a HFD (HFD + B + CrHis) provided the greatest levels of GLUT-1, GLUT-3, PPAR-γ, and IRS-1, but the lowest level of NF-κB in the brain and liver tissues.

CONCLUSION

Biotin supplementation with chromium complexes, CrHis in particular, to a HFD pose to be a potential therapeutic feature for the treatment of insulin resistance.

Comparative Effects of Estrogen and Phytoestrogen, Genistein on Testicular Activities of Streptozotocin-Induced Type 2 Diabetic Mice

The aim of this study was to compare the effect of synthetic estrogen (E2) with a phytoestrogen and genistein in ameliorating type 2 diabetes mellitus (T2D)-mediated testicular dysfunction in mice. The streptozotocin (STZ)-induced type 2 diabetic mice were treated exogenously with either E2 or genistein for 2 durations and compared their effects on testicular activities, serum glucose, and insulin level. Type 2 diabetic mice treated with E2 for only short term (14 days) improved regressive changes in the testicular histology by increasing testosterone synthesis and improving insulin sensitivity, whereas those treated for longer duration (28 days) failed to improve testicular dysfunctions. On the other hand, genistein treated for both short- and long term was useful in improving T2D-induced adverse effects on testicular functions. This study further suggests that treatment with genistein improves spermatogenesis in type 2 diabetic mice by increasing insulin-induced formation of lactate and antioxidative enzymes, which contributes to prevent germ cell apoptosis. Thus, genistein can be used to ameliorate T2D-induced testicular dysfunction.

Long-term complications of glycogen storage disease type Ia in the canine model treated with gene replacement therapy

BACKGROUND

Glycogen storage disease type Ia (GSD Ia) in dogs closely resembles human GSD Ia. Untreated patients with GSD Ia develop complications associated with glucose-6-phosphatase (G6Pase) deficiency. Survival of human patients on intensive nutritional management has improved; however, long-term complications persist including renal failure, nephrolithiasis, hepatocellular adenomas (HCA), and a high risk for hepatocellular carcinoma (HCC). Affected dogs fail to thrive with dietary therapy alone. Treatment with gene replacement therapy using adeno-associated viral vectors (AAV) expressing G6Pase has greatly prolonged life and prevented hypoglycemia in affected dogs. However, long-term complications have not been described to date.

METHODS

Five GSD Ia-affected dogs treated with AAV-G6Pase were evaluated. Dogs were euthanized due to reaching humane endpoints related to liver and/or kidney involvement, at 4 to 8 years of life. Necropsies were performed and tissues were analyzed.

RESULTS

Four dogs had liver tumors consistent with HCA and HCC. Three dogs developed renal failure, but all dogs exhibited progressive kidney disease histologically. Urolithiasis was detected in two dogs; uroliths were composed of calcium oxalate and calcium phosphate. One affected and one carrier dog had polycystic ovarian disease. Bone mineral density was not significantly affected.

CONCLUSIONS

Here, we show that the canine GSD Ia model demonstrates similar long-term complications as GSD Ia patients in spite of gene replacement therapy. Further development of gene therapy is needed to develop a more effective treatment to prevent long-term complications of GSD Ia.

Metabolic dysregulation accelerates injury-induced joint degeneration, driven by local inflammation; an in vivo rat study

Evidence is growing for the existence of an obesity-related phenotype of osteoarthritis in which low-grade inflammation and a disturbed metabolic profile play a role. The contribution of an obesity-induced metabolic dysbalance to the progression of the features of osteoarthritis upon mechanically induced cartilage damage was studied in a rat in vivo model. Forty Wistar rats were randomly allocated 1:1 to a standard diet or a high-fat diet. After 12 weeks, in 14 out of 20 rats in each group, cartilage was mechanically damaged in the right knee joint. The remaining six animals in each group served as controls. After a subsequent 12 weeks, serum was collected for metabolic state, subchondral bone changes assessed by μCT imaging, osteoarthritis severity determined by histology, and macrophage presence assessed by CD68 staining. The high-fat diet increased statistically all relevant metabolic parameters, resulting in a dysmetabolic state and subsequent synovial inflammation, whereas cartilage degeneration was hardly influenced. The high-fat condition in combination with mechanical cartilage damage resulted in a clear statistically significant progression of the osteoarthritic features, with increased synovitis and multiple large osteophytes. Both the synovium and osteophytes contained numerous CD68 positive cells. It is concluded that a metabolic dysbalance due to a high-fat diet increases joint inflammation without cartilage degeneration. The dysmetabolic state clearly accelerates progression of osteoarthritis upon surgically induced cartilage damage supported by inflammatory responses as demonstrated by histology and increased CD68 expressing cells localized on the synovial membrane and osteophytes. © 2017 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 36:881-890, 2018.

No Adverse Programming by Post-Weaning Dietary Fructose of Body Weight, Adiposity, Glucose Tolerance, or Metabolic Flexibility

SCOPE

Metabolic programming can occur not only in the perinatal period, but also post-weaning. This study aims to assess whether fructose, in comparison to glucose, in the post-weaning diet programs body weight, adiposity, glucose tolerance, metabolic flexibility, and health at adult age.

METHODS AND RESULTS

Three-week-old male and female C57BL6/JRccHsd mice are given an intervention diet with 32 energy percent (en%) glucose or fructose for only 3 weeks. Next, all animals are switched to the same 40 en% high fat diet for 9 weeks. Neither body weight nor adiposity differs significantly between the animals fed with glucose or fructose diets at any point during the study in both sexes. Glucose tolerance in adulthood is not affected by the post-weaning diet, nor are activity, energy expenditure, and metabolic flexibility, as measured by indirect calorimetry. At the end of the study, only in females fasting serum insulin levels and HOMA-IR index are lower in post-weaning fructose versus glucose diet (p = 0.02), without differences in pancreatic β-cell mass.

CONCLUSIONS

Our present findings indicate no adverse programming of body weight, adiposity, glucose tolerance, and metabolic flexibility by dietary (solid) fructose in comparison to glucose in the post-weaning diet in mice.

Male apoE*3-Leiden.CETP mice on high-fat high-cholesterol diet exhibit a biphasic dyslipidemic response, mimicking the changes in plasma lipids observed through life in men

Physiological adaptations resulting in the development of the metabolic syndrome in man occur over a time span of several decades. This combined with the prohibitive financial cost and ethical concerns to measure key metabolic parameters repeatedly in subjects for the major part of their life span makes that comprehensive longitudinal human data sets are virtually nonexistent. While experimental mice are often used, little is known whether this species is in fact an adequate model to better understand the mechanisms that drive the metabolic syndrome in man. We took up the challenge to study the response of male apoE*3-Leiden.CETP mice (with a humanized lipid profile) to a high-fat high-cholesterol diet for 6 months. Study parameters include body weight, food intake, plasma and liver lipids, hepatic transcriptome, VLDL - triglyceride production and importantly the use of stable isotopes to measure hepatic de novo lipogenesis, gluconeogenesis, and biliary/fecal sterol secretion to assess metabolic fluxes. The key observations include (1) high inter-individual variation; (2) a largely unaffected hepatic transcriptome at 2, 3, and 6 months; (3) a biphasic response curve of the main metabolic features over time; and (4) maximum insulin resistance preceding dyslipidemia. The biphasic response in plasma triglyceride and total cholesterol appears to mimic that of men in cross-sectional studies. Combined, these observations suggest that studies such as these can help to delineate the causes of metabolic derangements in patients suffering from metabolic syndrome.

Measurement of Intestinal and Peripheral Cholesterol Fluxes by a Dual-Tracer Balance Method

Long-term elevated plasma cholesterol levels put individuals at risk for developing atherosclerosis. Plasma cholesterol levels are determined by the balance between cholesterol input and output fluxes. Here we describe in detail the methodology to determine the different cholesterol fluxes in mice. The percentage of absorbed cholesterol is calculated from a stable isotope-based double-label method. Cholesterol synthesis is calculated from MIDA after ¹³ C-acetate enrichment. Cholesterol is removed from the body via the feces. The fecal excretion route is either biliary or non-biliary. The non-biliary route is dominated by trans-intestinal cholesterol efflux, or TICE. Biliary excretion of cholesterol is measured by collecting bile. Non-biliary excretion is calculated by computational modeling. In this article, we describe methods and procedures to measure and calculate dietary intake of cholesterol, fractional cholesterol absorption, fecal neutral sterol output, biliary cholesterol excretion, TICE, cholesterol synthesis, peripheral fluxes, and whole-body cholesterol balance. © 2016 by John Wiley & Sons, Inc.

Obesogen effects after perinatal exposure of 4,4'-sulfonyldiphenol (Bisphenol S) in C57BL/6 mice

Bisphenol A were removed from consumer products and replaced by chemical substitutes such as Bisphenol S (BPS). Based on their structural similarity, BPS may be obesogen like Bisphenol A in mice. Our objective was to determine the impact of BPS on lipid homeostasis in C57Bl/6 mice after perinatal and chronic exposure. Pregnant mice were exposed to BPS via the drinking water (0.2; 1.5; 50μg/kg bw/d). Treatment began at gestational day 0 and continued in offspring up to 23-weeks old. Then, offspring mice were fed with a standard or high fat diet. The body weight, food consumption, fat mass and energy expenditure were measured. A lipid load test was performed to check the postprandial triglyceridemia. Plasma parameters and mRNA gene expression in adipose tissues were also analysed. BPS induced overweight in male mice offspring fed with a HFD at the two highest doses. There was no change in food intake and energy expenditure. The overweight was correlated to the fat mass, hyperinsulinemia and hyperleptinemia. The plasma triglyceride clearance was significantly increased with BPS and tyloxapol(®) (triglyceride clearance inhibitor) reversed this phenomenon. BPS induced alteration in mRNA expression of marker genes involved in adipose tissue homeostasis: hormone sensitive lipase, PPARγ, insulin receptor, SOCS3 and adiponectin. This is the first time that BPS is described as obesogenic at low doses and after perinatal and chronic exposure in male mice. BPS potentiated the obesity induced by a HFD by inducing the lipid storage linked to faster lipid plasma clearance.

VEGFB/VEGFR1-Induced Expansion of Adipose Vasculature Counteracts Obesity and Related Metabolic Complications

Impaired angiogenesis has been implicated in adipose tissue dysfunction and the development of obesity and associated metabolic disorders. Here, we report the unexpected finding that vascular endothelial growth factor B (VEGFB) gene transduction into mice inhibits obesity-associated inflammation and improves metabolic health without changes in body weight or ectopic lipid deposition. Mechanistically, the binding of VEGFB to VEGF receptor 1 (VEGFR1, also known as Flt1) activated the VEGF/VEGFR2 pathway and increased capillary density, tissue perfusion, and insulin supply, signaling, and function in adipose tissue. Furthermore, endothelial Flt1 gene deletion enhanced the effect of VEGFB, activating the thermogenic program in subcutaneous adipose tissue, which increased the basal metabolic rate, thus preventing diet-induced obesity and related metabolic complications. In obese and insulin-resistant mice, Vegfb gene transfer, together with endothelial Flt1 gene deletion, induced weight loss and mitigated the metabolic complications, demonstrating the therapeutic potential of the VEGFB/VEGFR1 pathway.